Compensated valve gear



Oct. 9, 1934. R. CHILTON COMPENSATED VALVE GEAR Filed Oct. 15, 1950 2 Sheets-Sheet l INVENTOR. ROM/VD Cfi/L TON Oct 9, 1934-0 R. CHELTQN 1,976,433

COMPENSATED VALVE GEAR Filed Oci. 15, 1930 2 Sheets-Sheet 2 IN VEN TOR.

ROLfi/VD CHILTON Patented Oct. 9, 1934 UETE STATES COMPENSATED VALVE GEAR of New York Application October 15,

6 Claims.

My invention relates to valve gears in general and specifically to the type associated with radial air-cooled aircraft engines, wherein the valves are operated from a cam in the crankcase thru relatively long push rods and rocker arms pivoted in the cylinder heads. Due to the relatively great length of the cylinders and push rods, wide changes in valve clearance are developed under the varying expansion of the parts due to the wide variations in temperature encountered in operation. Constant valve timing and low impact velocities from the cam are incompatible with such wide clearance variations, which produce destructive loads on the entire mechanism.

The principal object of the present invention is to provide a compensated valve gear wherein there will be no change in clearance in spite of a large difference in expansion between the cylinders and the push rods. Another object of the invention is to provide a pivotally mounted rocker box construction which will retain lubricant for protracted periods. A still further object of the invention is to provide a durable means for mounting a rocker box for slight pivotal action about an axis normal to the valve axis, and which shall be rigid in all other directions and free from vibration. An additional object of the invention is to provide improved and readily accessible means for adjusting the valve clearances and one wherein the adjusting mechanism does not add to the weight of the moving parts.

To these ends the cylinder head is provided at each valve port with a pair of trunnions, spaced apart transversely of the valve axis, and each rocker box is provided with a pair of cooperating sockets, the rocker box being held down by a spring-clamped spherical seat which is concentric with the trunnions.

Tubular housings surround the push rods and are provided with spherical anchorages to the crankcase and rocker box respectively, one of these anchorages being adjustable to swing the rocker box on its trunnions and thus to adjust the valve clearance and to maintain the adjustment in spite of difierence in expansion in the cylinder and in the push rod.

In the drawings:

Fig. l is a section thru the axis of one of the so valves and of its associated push rod, and

Fig. 2 is a transverse section thru the cylinder in the plane of the pair of valves with the valve spring indicated in outside View.

Similar parts are given the same reference symbols in all views.

1930, Serial No. 488,704

Referring first to Fig. 2, 10 represents the cylinder head which is screwed to the barrel 12 in the usual way; 9 representing the usual piston. The cylinder head is provided with inclined valves 13 and 1% supported in guides 15, which are threaded at their outer or upper ends to receive nuts 16 which hold down the rocker boxes 17 thru the medium of a stiff spring washer 1S, engaging a spherical seating member 19 which in turn engages a complementary seat machined in the bottom of the rocker box 17. Each box is provided with a pair of opposed projections or lateral enlargements having cylindrical sockets 2o machined concentric with the spherical seat 19, and the cylinder head is provided with trunnions 21 against which the rocker box 17 is at all times firmly held under the pressure of the stifi spring washer 18. Due to the co-axial relation of the spherical seat and the trunnions, the rocker box is capable of slight rocking action about its axis, but due to the Wide separation of the trunnions it (the rocker box) is securely held from other motion and particularly from rolling and sideways vibration.

Referring now to Fig. 1, it will be seen that the rocker box 1'7 has an internally threaded ex tension 22 in which is engaged an adjusting nut 23 suitably locked as by a lock nut 24. The adjusting nut 23 has formed thereon or therein a spherical seat engaged by the head 25 of the push rod housing '26, which holds down the extended end of the rocker box to the crankcase 29. The function of the spring 27 is merely to keep the spherical faces in oil-tight contact when this tension member is not under load, i. e., when the valve is on its seat. The lower end of the push rod tube 26 is similarly anchored to the crankcase 29, but in this case, in place of an adjustable nut, a socket fitting 28 is secured to the crankcase 29 in any suitable manner. The tap-pet 31 may be of conventional design. The push rod 32 engages spherical seats in the tap-pet 31 and in one end of the rocker arm 33, the latter being pivoted in the rocker box at 34.

The other end of the rocker arm operates the valve thru a spherical ended strut 37, engaging spherical seats 35 and 36 in the rocker arm and at the bottom of the hollow part of the valve stem, respectively. This part of the construction and the special form of valve spring illustrated at 38, Fig. 2, and having arms 39 engaging in slots 40 in the valve stems, is the subject of co-pending application and need not be further described in this application.

The rocker box is provided with a quick detachable cover 41 held down by a hinged bar 42. drilled to receive the nut 43 of the swing bolt 44. By this construction the cover can be quickly swung open by merely slacking off on the nut 43 and disengaging the T head from the slot in the rocker box 17, while a gasket 45 insures an oil-tight joint.

It will be seen that by the spherical seating member 19 and the stiff disc washer 18, an oiltight seal is provided between the rocker box and the valve guide, and that this seal will be maintained in spite of slight expansion of the parts at operating temperatures. The joint between the push rod tube 26 and the rocker box 17 being similarly sealed, leakage at both points of articulation is prevented and lubricant placed in the box will remain effective on all the wearing surfaces for protracted periods.

The operation of the device is as follows:

The rocker box is pivotally mounted at the valve stem on the common axis of the trunnions 21 and the spherical seat 19 and its angular position on the cylinder head is con-trolled by the push rod tube 26 by which the outer end of the rocker box 17 is connected to the crankcase 29. This push rod tube 26 and the push rod 32 are preferably made of similar material, and as they operate at equal temperatures they will maintain the same relative length. On the other hand, the cylinders necessarily operate at much higher temperatures and the cylinder heads, due to expansion, move away from the crankcase as the engine warms up, which causes an increase in the valve clearance when the rocker box is rigid with the cylinder head. In

the present invention, on the contrary, the rocker box 17 changes its angle as the cylinders expand, thus affording compensation for this action without any change in valve clearance.

Previous attempts at compensation of valve gears by an articulated mounting of the rocker 'box have been abandoned because of difficulties encountered in obtaining a vibration proof and oil-tight joint trans-axial with the valve stem. In previous constructions loosening up of this joint, due to the heavy and rapid impacts to which it is subject and due to the destructive effects of expansion of the securing means, caused a reversion to the construction wherein the rocker box is integral with the cylinder head, thus eliminating the troublesome joint and securing oil tightness, but at the expense of a valve clearance variation as high as .060 in some of the larger engines, which seriously prejudices the efficiency and durability of the valve mechanism.

It will be seen that in the present invention a firmly secured and oil-tight rocker box is combined with complete compensation for cylinder expansion and that a compact and readily accessible mechanism is provided.

While I have described my invention in detail in its present preferred embodiment, it ,will be obvious to those skilled in the art after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

What I claim isf 1. In a compensated valve gear for internal combustion engines, a cylinder, a valve, a rocker box pivotally mounted on said cylinder, said rocker box having formed therein an opening thru which said valve extends, a rocker arm for actuating said valve enclosed within and movable both with and with respect to said rocker box, a push rod extended into said rocker box for actuating said rocker arm, a tubular housing within which said push rod is enclosed, an oiltight joint between said housing and said rocker box admitting of relative movement therebetween, and an oil-tight closure for said rocker box opening comprising a substantially spherical seat carried by said housing against which the rocker box is yieldingly held.

2. In a compensated valve gear for internal combustion engines, a cylinder, a rocker box pivotally mounted on said cylinder, a rocker arm enclosed within and movable both with and with respect to said rocker box, a tubular housing within which said push rod is enclosed, and an oil-tight joint between said housing and rocker box admitting of relative movement therebetween, said joint including a substantially spherical seat carried by said housing against which a. correspondingly shaped co-acting element is yieldingly held.

3. A pivotal mounting for a rocker box upon a cylinder having a valve comprising trunnions widely spaced apart transaxially of said valve, a substantially spherical seat in the rocker box, a co-acting seating member having a stiff spring, and securing means adapted to hold said spring to keep said trunnions in firm engagement despite slight expansion of the parts.

l. In a compensated valve gear for internal combustion engines, a crankcase, a cylinder, a valve, a rocker box pivoted on said cylinder, and a tubular housing having spherical anchorages with said crankcase and said rocker box, one of said anchorages being adjustable to swing the rocker box on its pivot.

5. In a compensated valve gear for internal combustion engines, a cylinder, a valve, a crankcase, a rocker box movable with respect to said cylinder, widely spaced bearings on said cylinder adapted to bear on said rocker box in a line normal to the valve axis and to the rocker box axis, and means concentric with said valve and with said bearings for resiliently holding said rocker box against said bearings.

6. In a compensated valve gear for internal combustion engines, a cylinder, a valve, a rocker box pivoted on said cylinder at relatively widely spaced points, said rocker box havin an opening formed therein at its extended end, a flanged push rod housing engageable in saidopening, resilient means for urging said housing from said opening, and a device engaging said flange to permit relative oscillation between said flange and said device, said device adjustably engaging said opening to hold said flange therewithin.

ROLAND CHILTON. 

